1. Field of the Invention
The present invention relates to an optical pulse generating apparatus for generating an ultrashort optical pulse signal such as a femtosecond (fs) optical pulse signal in an optical communication system and its manufacturing method.
2. Description of the Related Art
A prior art ultra-short optical pulse generating apparatus using titanium doped sapphire laser generating apparatus using broadband characteristics of a gain medium of titanium doped sapphire crystal (see: JP-2003-500861 A corresponding to WO 00/72412 A1).
The operational principle of the above-mentioned titanium doped sapphire laser generating apparatus is based upon self-phase modulation due to the optical Kerr effect of titanium doped sapphire crystal per se. According to the optical Kerr effect, when the intensity of incident laser light is small, the refractive index of laser crystal is small, while, when the intensity of incident laser light is large, the refractive index of laser crystal is large.
However, the above-described titanium doped sapphire laser generating apparatus is very large in size and high in manufacturing cost.